1. Field of the Invention
The present invention relates to a capacitor structure formed in an integrated circuit on a semiconductor substrate.
2. Description of Related Art
As a conventional example of capacitor structure formed in an integrated circuit on a semiconductor substrate, an interdigital capacitor structure is known in which a pair of opposing electrodes in the shape of a comb are placed with their teeth interdigitated with each other. In this capacitor structure, capacitances are respectively formed between the corresponding teeth. In other words, since the surface area of the opposing electrodes increases, a large-capacity capacitor can be obtained in the same area compared with a simple parallel plate capacitor (see Japanese Laid-Open Patent Publication No. 4-268756 (page 3, FIG. 1), for example).
However, in the conventional capacitor structure described above, the capacitance is formed in the tooth portions of the comb electrodes, not in the base line portions thereof. Therefore, the capacitance may include an inductance component and an electric resistance component, although minute in quantity, between the teeth portions and the base line portions. For this reason, for a capacitor used for the purpose of noise removal between the two electrodes, such as a bypass capacitor, for example, the noise attenuation characteristic may not be sufficient in a high-frequency range. In view of this, with the trend toward finer and faster integrated circuits, improvement in capacitor characteristics has become necessary.